The present invention generally relates to inflation devices. More specifically, the present invention relates to inflation devices such as syringes used to inflate and deflate balloon catheters.
Balloon catheters are sometimes inflated with gas, rather than liquid, because the balloon can be inflated and deflated more quickly than a comparable volume of saline or other liquid inflation media. Gas inflation has proved particularly useful in inflation of balloon centering catheters used in radiation therapy, which relies on a centering balloon to prevent the radiation source from being too close to one side of the target vessel. The use of gas rather than liquid decreases the amount of attenuation of radiation between the radiation source and the vessel wall.
While gas filled balloons are advantageous in some situations, the prior art process of preparing an inflation device for gas inflation is much more complicated than that for liquid inflation. Although air would be relatively easy to load into an inflation device, air is not a suitable inflation medium, because air does not rapidly dissolve in blood. In the event that the balloon bursts or leaks, bubbles could be formed in the arterial blood, impeding blood flow. In addition, a chief component of air, nitrogen, is not desirable for balloon inflation because nitrogen gas has thrombogenic properties which may present clinical risks in the event that the balloon bursts. Accordingly, it is desirable to use a gas other than air and to prevent air contamination of the gas used. A preferable gas used for balloon inflation is carbon dioxide.
Many medical facilities have built-in plumbing systems that provide gases such as carbon dioxide. Alternatively, a pressurized gas canister of carbon dioxide may be used. In either case, the pressurized source of carbon dioxide must be connected to a reduction valve to fill the inflation device with gas. The reduction valve lowers the pressure of the gas to a pressure suitable for the syringe. The reduction valve may utilize several stopcocks that must be opened for the gas to flow. For example, a first stopcock may be located at the reduction valve, a second stopcock may be located at the catheter connection point, and a third stopcock may be located at the syringe. Such systems are physically cumbersome and unwieldy, and require considerable preparation time by skilled medical personnel. Accordingly, a desirable feature in an inflation device would be an inflation syringe preloaded with a specified gas which the physician could conveniently use without extensive preparation and equipment.
Unfortunately, however, the storage of gas in a syringe mechanism presents several difficulties. Most plastics used in syringe manufacture are gas-permeable, at least to some extent. In addition, most stopcocks and syringe plungers, even when manufactured to precise specifications, are subject to leakage over extended periods of storage. Finally, packaging materials used to maintain sterility are usually gas permeable to facilitate ETO sterilization. These factors contribute to loss of the stored gas and/or contamination of the stored gas by air.
To address these problems, related U.S. patent application Ser. No. 09/644,754, filed Aug. 23, 2000 entitled PRELOADED GAS INFLATION DEVICE FOR BALLOON CATHETER discloses a number of different inflation devices preloaded with an inflation gas (other than air). Such inflation devices generally include a barrel defining a chamber preloaded with the inflation gas, and include some means for preventing air contamination of the inflation gas.
To further address these problems, the present invention provides several embodiments of an alternative inflation device. The present invention generally provides inflation devices that are preloaded with a fluid (e.g., a gas other than air) stored in a chamber in the plunger. By utilizing a storage chamber defined by the plunger, the present invention makes use of space that is otherwise underutilized and may be more readily protected against contamination.
For example, an inflation device in accordance with one embodiment of the present invention includes a barrel defining a primary chamber therein, a plunger disposed in the primary chamber and defining a storage chamber, and a valve for selectively providing fluid communication between the storage chamber and the primary chamber. The preloaded fluid may be pressurized and may comprise, for example, a gas (other than air), a liquid, or a fluid containing a drug. The inflation device is preferably preloaded by the manufacturer and/or packager of the inflation device.
The inflation devices of the present invention are suitable for inflating and deflating a wide variety of balloon catheters such as a centering balloon catheter or an angioplasty balloon catheter. The inflation device of the present invention is particularly useful in a medical system for intravascular delivery of ionizing radiation using a centering balloon catheter. In addition, although described with specific reference to a syringe type inflation device for purposes of illustration, other closed volume inflation devices are within the scope of the present invention.